Use local eggs for building and installing

* Check in a cache dir each for zc.buildout and distribute
* Check in downloaded copies of external dependencies (bootstrap.py, ez_setup.py, distribute.py)
* Edit bootstrap.py, Makefile and buildout.cfg to not do downloads
* Edit development.md to remove PyPI dependencies there
* Fix missing libxml2-dev build dependency

I've tested the build and install of homer and homestead on a new AWS instance with /etc/hosts configured so that pypi.python.org is 127.0.0.1, and it seems to work using these changes.